Retirement benefit plan, Changes in Fair Value of Plan Assets (Details) - Domestic Defined Benefit Plans [Member] - CHF (SFr) SFr in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in fair value of plan assets [Abstract]
Interest income	SFr 55	SFr 56	SFr 76
Employer's contributions	(590)	(511)	(441)
Fair Value of Plan Assets [Member]
Changes in fair value of plan assets [Abstract]
Fair value of plan assets, beginning of period	7,798	6,652	5,681
Interest income	55	56	76
Employees' contributions	528	436	375
Employer's contributions	590	511	441
Benefits payments	426	111	48
Plan assets gains/(losses)	(45)	32	31
Fair value of plan assets, end of period	9,352	SFr 7,798	SFr 6,652
Fair Value of Plan Assets [Member] \| 2018 [Member]
Changes in fair value of plan assets [Abstract]
Employer's contributions	SFr 630

No definition available.

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- Definition

The increase in the net defined benefit liability (asset) resulting from the passage of time.

+ References

No definition available.

+ Details

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- Definition

The decrease (increase) in net defined benefit liability (asset) resulting from contributions to a defined benefit plan by the employer. [Refer: Net defined benefit liability (asset); Defined benefit plans [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2016-01-13
-Paragraph 141
-Subparagraph f
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2016-03-30&anchor=para_141_f&doctype=Standard
-URIDate 2016-03-31

+ Details

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- Definition

The decrease (increase) in the net defined benefit liability (asset) resulting from contributions to a defined benefit plan by plan participants. [Refer: Net defined benefit liability (asset); Defined benefit plans [member]]

+ References

+ Details

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- Definition

The decrease (increase) in the net defined benefit liability (asset) resulting from payments from the plan. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2016-01-13
-Paragraph 141
-Subparagraph g
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2016-03-30&anchor=para_141_g&doctype=Standard
-URIDate 2016-03-31

+ Details

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- Definition

The fair value of defined benefit plan assets. Plan assets comprise assets held by a long-term employee benefit fund and qualifying insurance policies. [Refer: At fair value [member]]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 19
-IssueDate 2016-01-13
-Paragraph 57
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2016-03-30&anchor=para_57_a&doctype=Standard
-URIDate 2016-03-31

+ Details

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- Definition

The decrease (increase) in the net defined benefit liability (asset) resulting from the return on plan assets. The return on plans assets is interest, dividends and other revenue derived from the plan assets, together with realised and unrealised gains or losses on the plan assets, less any costs of managing plan assets and less any tax payable by the plan itself, other than tax included in the actuarial assumptions used to measure the present value of the defined benefit obligation. [Refer: Plan assets [member]; Net defined benefit liability (asset); Actuarial assumptions [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2016-01-13
-Paragraph 141
-Subparagraph c
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2016-03-30&anchor=para_141_c_i&doctype=Standard
-URIDate 2016-03-31

+ Details

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- Details

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